Means for regulating the rate of fire of automatic firearms



G. IRONSIDE MEANS FOR REGULATING THE RATE OF FIRE OF AUTOMATIC FIREARMS G. IRONSIDE Nov. 28, 1944.

MEANS FOR REGULATING THE RATE OF FIRE OF AUTOMATIC FIREARMS 2 Sheecs-Sheell 2 Filed March 25, 1942 Patented Nov. 28, 1944 MEANS FR REGULATING THE RATE F FIRE 0F AUTOMATIC FIREARMS George Ironside, Hartford, Conn., assigner to Colts Patent Fire Arms Manufacturing Company, Hartford, Conn., a corporation of Con necticut Y' Application March 25.1942, serial No. 436,14 Q

6 Claims. l (Cl. 89-3) This'invention relates to means for regulating the rate of ring of automatic rearms and more particularly to means for varying said rate of firing.

In automatic rearms constructed only for free,

automatic firing and having no means included for regulating the rate of ring thereof, overheating of various parts of the rearms, and particularly the barrel, will usually occur so that some form of cooling means is required in order to enable the gun to be continuously fired for reasonably long periods of time and for other than short bursts of fire. Furthermore, when an automatic rearm res too rapidly, there is a tendency on the part of the firearmv to vibrate in various directions whereby the accuracy of the gun is impaired due to the inability of the operator to hold the rearm suiiiciently still to accurately aim it. This tendency of the gun results in wasting ammunition.

It is the object of the present invention to provide in an automatic firearm a retarding means which will produce a rate of fire considerably slower than the rate of fire resulting where no retarding means is used whereby the barrel of the firearm may be cooled by air rather than a water jacket and, due to the slower rate off lire, the accuracy of the firearm is enhanced with the `result that waste of ammunition means, improved means for guiding some of the' various movable parts and the particular ,arrangement, and construction of the breech bolt engaging means, all of which details and the advantages thereof as well as other objects of the invention will be described with more par- `ticularity in the following speciiication:

The accompanying drawings show the embodiment of the invention which is deemed preferable, but it will be understood that the drawings are intended for illustrative purposes only and Fig. 1 is a side elevation of an automatic rearm including the breech bolt retarding mechanism `forming the subject matter of the invention, the breech casing of said firearm being partly broken away to disclose the retarding mechanism.

Fig. 2 is a fragmentary sectional elevation taken on the line 2 2 of Fig. 1 and is on a larger scale than in Fig. 1.

Fig. 3 is a fragmentary side elevation, partly in section, taken on the line 3-3 of Fig. 2 showing details of the retarding mechanism and the breech bolt in fully recoiled position.

Fig. 4 is a side elevation similar to Fig. 3 but showing the breech bolt forward of its position in Fig. 3 and about to `be released by the retarding mechanism, the arrow on the breech bolt indicating the direction of travel thereof.

Fig. 5 is a plan view of details of the lock frame and the retarding mechanism and also fragments of other parts in the breech casing with all of the parts in the same relative position as in Fig. 3.

Fig. 6 is a fragmentary side elevation showing the breech bolt in a position during movement in recoil direction as indicated by the arrow, the breech bolt depressing the pawl of the retarding mechanism while so moving.

Fig. 7 is a fragmentary side elevation similar to Fig. 6 but showingthe breech bolt in a position during movement in counter-recoil direction as indicated by the arrow, the breech bolt having just engaged the pawl of the retarding mechanism.

Fig. 8 is a side elevation of a combined escapement and ratchet wheel.

Fig. 9 is a front elevation of the combined escapement and ratchet wheel.

Figs. 10, 11 and 12 are respectively rear, side and front elevations of the escapement weight included in the retarding mechanism.

Figs. 13 and 14 are respectively a plan and side elevation of the movable pawl carrying member in the retarding mechanism. Y

, Fig. l5 shows end and side elevations of one member of a separable pin device for guiding the movable member shown in Figs. 13 and 14.

Fig. 16 shows end and side elevations of another mem-ber of said separable pin device which cooperates with the member shown in Fig. 15.

Figs.4 17 and 18 are respectively a plan view and a side elevation of the adjustable pawl of the retarding mechanism.

Fig. 19 is a fragmentary elevation taken on the line IB-IS of Fig. 7 showing a detail of a portion of the breech bolt.

The subject matter of the present invention and other parts and portionsfofm'achi'ne which are illustrated in detail in other patents such as U. S. Patent 1,293,021 to Browning, and U. S. Patent 1,628.226 to Browning. Referenceifs; made to said patents for an explanation of the details illustrated in the present drawings but not described. VIt'fis believed, however, that'anyone skilled'in the art will readily recognizeV the function of these detailswhich arenillustratedbut not described,-andsince they constitute no part of 'the presentinvention it isa-believed that a description of the same is unnecessary.

, Operably included in the breech casi-ngV are reciprocable barrel extension I4 4and breech bolt I6, the breech bolt having a depending projection I8' which extends below the lowerv surface of: the remainder ofi the Vbreech bolt andi` one of the normal functions thereof is-*t'oco-act with the accelerator V` in a manner similar to'thatv described in above referred'to Patent 1,628,226. The breech bolt i6 isreciprocable in the breech receive projecting guide lugs 40 which are integral, with and project outward from the side plates 34 and 36 of the lock frame. The guide lugs 40 primarily prevent upward or downward transverse movement of the lock frame with respect to the breech casing.

A spacingsleeve 42 is fixed to and disposed between the side plates adjacent the rear end of each. Slideably disposed withinand normally spring pressed outward toward one end of said 'spacing sleeve is a lockingY plunger 44'which excasing between full recoil and" firing positions. v

The explosion produced upon ring the cartridge generatesl the'f'orcejto move'the breech boltin recoil direction while'driving spring IT forces the breech'bolt in counter-recoil direction to {firingposition. The accelerator 20'al`so cooperates with the barrelv ,extension projection -2'2Y in a manner similar tov thatdescribed'inv said patent. The barrel extension'projection 22A has a member 24 extending laterallytherefrom at one side for engagement by thebarrel plunger 26 which is normally resilientlyurged forward` by springA 28.

When the barrel extension-is in retracted or fully recoile-d positionas shown in-Figs.' 3 and 4, the

laccelerator locksthe barrel'extension in its" rearmost position and holds the spring 28compressed. The barrel plunger 2S has a, suitable shaft 30 which is surrounded by the spring 28.

A lock frame generally designated as 32' and comprising side plates t4V and" 3.6' is disposed in the rear portion ofthe breech casing. Mounted between and'unitedV withthe `side, plates isa spacing plate 38 having .a suitable aperture through whichthespring'z and .shaft 30 project asbest shown in-Fig. 3.. The accelerator 2B is also pivotally mounted between the side plates of the lock frame. y

The lock frame32 vcarries the entire breech bolt ,retarding mechanism as a unit. The lock frame'isv readily removable fromthe, rear of the ybreech casing, after the .backvplateassembly has been removed, whereby the .acceleratorv mechanism may bereadily removed for any `desired lpurpose such aszinspection or forreplacement of parts. The conventional side plates of the breech casing l2 are each provided with a longitudinal rgroove 39 on the inner face thereof whereby a vpair of oppositely disposed groovesv are provided on the interior of the breech `casing to sldeably 4tends through and `projects outward beyond the y side plate 3B.

The locking plunger 44 is receivablein a suitable aperture 46 provided in the adljacent side plate of the Ibreech casing to prevent longitudinal movement of the lock frame with respect to the 4breech casing. IThe outer end of the locking plunger 44 is therefore adapted to be engaged from the exterior of the breech casing by any suitable tool or implement and pressed inward to-free it from the aperture 46 inthe vside plate:r ofthe breech casing following which thelockframe assembly may be removed rearward from the breech casing for the above men- 4tionedA purposes.

Also ymou-nted'between thesid'e lplates of the l'ock'frame and disposedy in a suitable notch 48 arranged in' the upper portion ofl the spacing plate 38 isa trigger bar 50 movably mounted on a pivot 52. As shown in Fig. e, the trigger bar is adapted to be actuated by the trigger 53.

A Vshoe or pawlcarrying member 54l is reciprocably mounted for guided movement between the `side plates of the lock frame.` The path of said shoe is in a substantially straight line extendingforward and downward in the lock frame which directions are with respect to the breech casing in which 'the barrel end of the breech casing is lconsidered the forward end thereof. The term downward is considered with respect to the position of the Yiirearmshcwnv in Fig. l.

The means producing or controlling` the guided 'movement ofthe shoe 54 consist of: a pair oi apertures 56 provided in the shoe; a pair of slots 5B formed in they side plate 36' with the slots disposed at an angle to the longitudinal edges of the side plate and parallel to each other and also to the line oi movement oi" the shoe; and

a `pair of guide sleeves or pins G0 which are in the nature of slideable guide bearings and are disposed' through the apertures 5G'in the shoe and the guide'slots 5i! in the side plate 35. The guide slots 58 illustrated herein are disposed at an `angle of approximately fifteen degrees to the .longitudinal edges of the side plate 35.

`This angle has been found to produce satisfactoryresults butv the same is to be interpreted as descriptive and not restrictive since a variance either way in the angle willv produce passable results. 'Each pin 6B is a composite member formed of a sleeve 62 provided with a head having a counterbored annular shoulder 64 disposed therein and aheaded split pin 66 having an enlarged er1-d opposite the he-ad which forms laterally projecting detents 68. By inserting the A kenlarged end ofI the split pin 66 in the unheaded 4end oi the sleeve 62, the detents of the split pin .will be, compressed toward each other until such time, as, the pin E6 is completely inserted withinthe sleeve 62 when the detents 68 will clear the interior of the sleeve 62 and move awayv from each other to engage the annular shoulder 64 of `the headed sleeve 62. The oute-r end of each detent 68 is rounded and tapered, as

yto the shoe.

well shown in Fig. 16, -for purposes of being engaged by a suitable annular tool which may be pressed against the tapered portion of the detents to force them together to clear the annular shoulder 64 of the sleeve 62 to permit the disengagement of the slotted pin 66 from the sleeve`62,

It will thus be seen that the shoe 54 is adapted to be quickly secured to the side plate 36 for reciprocable guided movement with respect thereto and in View of the particular locking means provided in the guide pins 68 for holding the composite parts thereof together, said pins will not become disengaged due to general use, vibration, or jarring incident to the manipulation and operation of the machine gun. However, when it is desired to remove the shoe from the side plate for any purpose desired, the re. moval of the shoe is readily accomplished due to the quickly detachable nature of the composite guide pins 60.

The width of the slots 58 is adequate to receive the diameter of each of the guide pins 60 without appreciable wobble or loosenessv in order to eliminate lost motion and consequent chatter incid-ent to the movement of the shoe 54 in operation. Only sufcient clearance is provided, however, to permit smooth sliding movement of the guide pins 60 within the slots 58.

The perimeter of each slot 58 adjacent the outer surface of the side plate 36 is provided with a recessed shoulder 10 which extends uniformly around the perimeter of each slot to accommodate the head of the slotted pin 66 provided on each of the guide pins 60 whereby the one side of said shoe as shown in Fig` 13, toA

receive a pivoted pawl to be described. The shoe 54 is also provided adjacent one end with a slot '|4 extending longitudinally of the shoe and opening upward and outward toward said end to provide a pair of ears 16 through each of which an a pusher type pawl and the design thereof is aperture 56 extends. A slot or recess 18 is also provided in the shoe 54 in the under side thereof adjacent the `opposite end, as best shown in Figs. 4 and 14, to pivotally receive and mount one end of a ratchet rack to be described. The pivot for said rack consists of a pin extending through the side portions of the shoe 54 disposed on opposite sides of the recess |8.` The shoe 54 also has a projection 82 extending longitudinally outward from one end thereof which projection provides a surface with which an adjustment screw, to be described, is adapted to engage.

A breech bolt yengaging dog or pawl 84 is pivotally mounted on and carried by the shoe 54. The pawl has a central portion 86 reducedin width and containing a bearing aperture 88. The reduced central portion of tliepawl is received between the upstanding ears 76 of the shoe 54 and one of the guide pins 68 extends through the apertures 56 in the ears i6 and the bearing aperture 88 of the pawl to pivotally connect the'pawl One end of the pawl is formed as a breech bolt engaging portion 99. The upper surface 92 thereof is relatively long and is provided with a smooth finish whereby, when the breech bolt is moving in recoil direction, it will engage the pawl with a free sliding movement over the upper surface 92 and, in so doing, the movement of the breech bolt will not be encumbered. Also, in view of the relatively large area afforded by upper surface 92, no appreciable amount of wear will take place on this portion of the pawl due to the breech-bolt sliding thereover. Furthermore, this breech bolt engaging end of the pawl is hardened, when finished, to a relatively high degree to further resist tendency to wear.

The other end of the pawl has an irregular contour, as shown in Fig. 18 particularly, and is .provided with a slot 94 extending inward from the end and terminating in a threaded aperture 96 lprovided in said end of the pawl to receive a threaded adjustment screw 98 for purposes to be described. The slot 94 provides a pair of eX- tending wings |00, one of which contains a countersunk aperture |82 and the other a threaded aperture |84, which apertures receive a headed locking screw |06 adapted to clamp said wings about the adjustment screw 98, after the same has been adjusted to the desired position, to maintain said adjustment. Adjustment screw 98 is made accessible through the forward slot 58 by removing the lock frame assembly from the breech casing.

The under side of the breech bolt engaging portion or end of the pawl 84 is provided with a circular recess |08 to receive one end of a. coil compression spring lll), the otheI` end Vof which is received in a circular recess 2 in the base of the recess'a I2 in the shoe 54. The spring H0' normally urges the breech bolt engaging end of the pawl into proper position to engage the breech bolt during a portion of the counter-recoil movement of said breech bolt prior to the return of the latter to full firing position. The upper limit to which the breech bolt engaging portion of the pawl may be elevated is controlled by a stop formed on the under side of the reduced central portion 86 'of the pawl which stop is adapted to engage the base of the slot 14 formed in the shoe 54.

It will be observed that disposing the pivot for the pawl forward of the breech bolt engaging portion 90 produces what might be termed such that as the breech bolt pushes against the pawl while moving in counter-recoil direction, the pawl will be urged all the more into engagement with the substantially vertical surface on the breech bolt projection I8 which is engaged by the pawl. With this design, even should the breech bolt engaging portion 90 of the pawl become worn, positive engagement between the 'projection I8 and the portion 98 of the pawl is still insured, thus resulting in long lifefor the pawl.

Previous to its engagement by the breech bolt depending projection I8, the pawl 84 projects upward above the upper edges of the lock frame and the upper surface of the shoe 54 as best shown in Figs. l, 3 and '7. The extent to which the end 99 extends upward depends upon the adjustment of the screw 98. Said screw is of adequate length that when desired, it may be threaded downward into the pawl suiciently to coact against the` projection 82 of the shoe 54 and withdraw the breech bolt engaging end into the recess 12 sufliciently so that it will be completely below the upper surface of the shoe 54 and not engage the breech bolt in its reciprocylindrical shaft |22.

cablel movement: in;..the breech. casing; When in suchwithdrawn position, theV pawl-will thus render thE retard-ing -mechanism inoperative and the; machine may then` reat full, or nonretarded, speed. ,i

As is obvious from Fig. 6 vthe dimensions of the adjustmentsc-rew 98are such Ythat when the breech boltmoves in recoil direction' and cams the-pawl downward into the recess l2, the upper end4 of the screw will not interfere with such movement of the breech bolt.

The spacing plate 38 is formed with a block 4 extending forward thereof and containing a circular bearing aperture ||6 extending therethrough at an angle to the horizontal and parallel toy the slots 58 in the side plate 36. Loosely mounted.- in a rcircular recess ||8 in ther projection 82 .of the shoe is a reduced `end |20 of a The diameter of the reduced end |fgis slightly less than the diameter of the circular recessl I8 whereby asmall amount block ||4 and the end ofthe projection 82 to normally resiliently urge the shoe 54, and pawl carried thereby,` to itsl uppermostand rearmost position. 'I'heshaft |22 is'primarily for the pur- Y pose of maintaining the-spring |26in proper alignment and in operative position. A combined member, having an escapement wheel or gear |28 and. aratchet wheel or gear |30. similar to a pinion gear, is mounted for rotatable movement on a xed shaft |32l extending between theeside plates. `In the preferred embodiment of the invention, the combined wheel is formed from a single piece of stock, but it is to be understood that it may be formed in any other manner such as by making the escapement and ratchet wheels separately and suitably securing them for movement in unison. The combined wheel` is shown in detail in Figs. 8 and"9.

An escapement weight |34, details of which are shown in the various views in Figs. 10 through 12, is also mounted for oscillatory movement about a fixed shaft |36 extending between the side plates. In order that the size of the breech casingmight be maintained at a minimum and y'et. to the end that the Amaximum amount of required weight might be afforded the escapement weight, the latterhas been designed with a somewhat irregular configuration, as will be observed from Figs. 10 through 12 especially, in order that the escapement weight may be tted into the design of the lock frame and be free tomove with respect to the remainder of the retarding mechanism included therein. be observed, for example, that one weight proclucingr portion |38 is relatively narrow and eX- tends upward and rearward, clearing thel spacing sleeve 42, the shoe 54, and the trigger bar 50. Another weight producing portion `|40 is wider than portion 38 and also extends rearward, clearing the spacing sleeve 42.

Spaced escapement teeth |42 are arranged on one face of the escapement weightand are adapted to co-act with the teeth ofthe escapement wheel I 28, the spacing of the teeth |42 being It will' aaeaocc;

suchthat an oscillatory movement is produced inthe escapement Weight as the escapement wheel |28 is moved in a given direction past and into engagement with the escapement teeth |42. The escapement mechanismjust referred to comprising the escapement wheel |28 and escapement weight |34 might be termed a retarder device. l

It might be said that the portions |38 and |40 constitute the main weight producing portions of the escapement weight and it will be noted that fthese portions, for the mostpart, extend substantially horizontallyl when'the rearm is in normal firing position whereby the function of the escapement weightxis enhanced due toxthe force of vgravity tending to move the escapement in onedirection atall times whenv the, firearm .is operated in or substantially in `the position shown in Fig. 1. The total mass of the escapement weight is suicient, however, that the function of the escapement mechanism will be satisfactory when the rearm is heldV in otherl positions than the one referred to'above.

A rack |44r for connecting theY escapement mechanism to the shoe 54 is mounted on the shoe for movement therewith in the reciprocatory path ofl the shoe. The rack, however,' is otherwise oatingly mounted with respect to the shoe whereby the rack is free tov move within certain limits in a direction substantially transverse to the line of reciprocatory movement of the shoe. The construction permitting this consists of a slot |4u` extending inward transversely from one side of the rack. at one end thereof. Said slot extends about the pin 80 projecting through the shoe 54 and. the recessA 18 formed therein, which recess receives the end of the rack ycontaining the slot |46. Theface of the rack opposite that having the ratchet .teeth is formed with a plurality of circular recesses 48. `Similar. recesses are formed in the adjacent face of the shoe, the opposed recesses |48 and |50 receiving compression springs |52 therebetween to normally resiliently urge the ratchet teeth of the rack into engage- -ment with the teeth of the ratchet wheel |30. f

When the "shoe 54 is moving forward `and downward due to the guide slots 58-and the action of the breech bolt engaging the pawl 84 when the breechbolt is movi-ng forward in counterrecoil, direction, the rack |44 engages the ratchet gear |30 which in .turn rotates the escapement wheel |28 and this inturnwobbles or oscillates the escapementweight about its pivot to produce a retarding effect upon the movement of the shoe 54 in the direction described. When the shoefis so moved, the spring |26 is also being compressed. v

Upon the release of the forward rface of the depending projection I8 of thebreech bolt by the pawl 84, the spring |26, being vrelatively strong,A quickly moves the shoe 54 rearward and upward to its normal position of repose. The

`pawl 84, in the interim, is depressed progressively into the recess 'I2 of the shoe as long as the shoe continuesto moveupward and rearward and the depending projection I8 of the breech bolt remains in engagement with the pawl while moving forward thereover in counter-recoil direction. Immediately upon. the projection I8, clearingthe pawl, the spring I0 .will press the end 00 upward. l During the upward and .rearward movement of the shoe, the springsl |52 will yield to permit the rack |44 to ride over the teeth of `the ratchet wheel |30 whereby, during the so-called return movement of the shoe, the escapement mechanism is not actuated except as some possible incidental frictional engagement between the teeth of the rack and the ratchet wheel might actuate the escapement mechanism to a limited extent. The engagement of the pin 80 on the shoe with the slot |46 of the rack insures the positive return of the rack to starting position with the shoe. The slot |46 also permits ready and quick assembly of the rack with the shoe.

A supplementary retarding effect is produced in a further embodiment of the present invention by the provision of a notch |54 in the under face and at one side of the depending projection I8 of the breech bolt, clearly shown in Figs. 7

and 19. After therbreech bolt has travelled for-n ward suiiciently in counter-recoil direction to have the projection I 8 released by the pawl 84, the spring |26 immediately proceeds to restore the shoe and pawl to starting position. During the `continued counter-recoil movement of the projection I8 on the breech bolt, the spring ||0 will urge the pawl 84 upward into the recess |54 and 4the rearmost wall of the notch |54 will promptly be engaged by the pawl 84 to again exert a retarding effect on the breech bolt as it continues to move forward during which continued movement the pawl will again be progressively moved forward and downward until it is out of engagement with the rear wall of the recess |54, following which the breech bolt may continue its forward or counter-recoil movement independently of the retarding effect produced yby the escapement mechanism described above and the shoe and pawl will again be restored to their position of repose.

The operation of the retarding mechanism is as follows:

Assuming the breech bolt is forward in firing position and the cartridge has just been fired, the` force of the resulting explosion moves the breech bolt and barrel extension rearward until they are disconnected, following which, the accelerator 20 rapidly moves the breech bolt to full recoil position, shown in Fig. 3. The accelerator locks the barrel extension in fully retracted position. The shoe 54 now is in the uppermost and rearmost position shown in Fig. 3. When the projection I8 of the breech bolt moves past the pawl 84 in recoil movement, the pawl will be depressed into the position illustrated in Fig. 6. As soon as the projection I8 has passed over the pawl, the spring I l restores the pawl to the position shown in Fig. 3.l Following the breech bolt reaching full recoil position, the driving spring I'I moves the breech bolt in counterrecoil direction toward firing position and the projection I8 engages the pawl 84 to cause the force or effect of the retarding mechanism to oppose the force of the driving spring I'I to delay the return of the breech bolt to firing position. The initial engagement between the projection I8 and the pawl 84 appears as shown in Fig. 7. With the continued forward movement of the breech bolt projection I8 in counter-recoil direction, the shoe 54 carrying the pawl moves forward and downward and progressively moves the engaging portion 90 of the pawl downward across the substantially vertical face of the projection I8 until the breech bolt and the projection I8 reach the position shown approximately in Fig. 4 wherein the pawl is at the point of releasing the projection I8 to free the same from the eiect of the retarding mechanism. During the time the pawl is in engagement with the projection I8, and is moving forward therewith, the rack |44 is being moved forward and downward by the shoe, the rack rotating the ratchet Wheel |30 and simultaneously the escapement Wheel |28 Wobbles or oscillates the escapement weight and produces a retarding effect or drag on the movement of the shoe in its forward path. Immediately following the disengagement of the pawl from the projection I8, the breech bolt may proceed forward independently of the effect of the escapement mechanism under the influence of the driving spring I'I. The projection I8 next engages the accelerator 20 to unlock the barrel extension and permit the spring 28 to urge the barrel extension forward to ring position.

As soon as the pawl has released the breech bolt, the spring |28 immediately begins to restore the shoe 54 to upper and rearmost position shown in Fig. 3. The movement of the shoe upward and rearward while the projection I8 is still moving thereover forces the pawl progressively downward into the recess |2 until the projection I8 has passed thereover, following which, the spring I |0 restores the pawl to the position shown in Figs. 1 and 3. During the upward and rearward movement of the shoe 54 the rack resists the force of the springs |52 and rides over the ratchet Wheel |38 whereby, under normal circumstances, the escapement mechanism is not actuated during the return movement of the shoe and rack due to which the return of the shoe is more rapid than if the rack only moved in a fixed longitudinal path and did not disenggae the escapement mechanism. In addition, the wear on the escapement mechanism is saved during the return movement of the shoe and the rack.

As described in the foregoing, the pawl is provided with adjustment means to permit the varying of the amount of engagement which will take place between the pawl and the projection I8 of the breech bolt. The varying of said engagement will directly affect and control the amount of movement of the breech bolt in counter-recoil direction during which the pawl remains in engagement with the breech bolt. This adjustable or varying function may also be described in terms of a time interval during which the breech bolt is in engagement with the pawl since, obviously, any adjustment in the screw 98 on the pawl will vary the interval of time during which the breech bolt is retarded by the escapement mechanism. The locking screw |06 for the adjustment screw 98 is accessible through the forward slot 58 in the lock frame for manipulation by a screw driver or other suitable tool as is clearly seen from Fig. 1.

When it is desired to further retard or slow down the rate of ring of the machine gun over the retarding aiorded by the pawl 84 during one engagement with the breech bolt within the range afforded by the adjustment mechanism of the pawl, one or more notches |54 such as illustrated in Fig. 7 may be formed in the under side of the breech bolt projection I8 to cause the retarding effect of the escapement mechanism to be reacted against the breech bolt and the force of the driving spring II a plurality of times. Thus the amount of retarding which may be produced or included in a machine gun by the mechanism illustrated and described in this application has a relatively wide range.

It will thus be seen that the mechanism included in the present invention includes, among other benecial and improved features, a retardadjustability; guide means' for certain movable parts of the ret-arding mechanism which yeiectively align said parts during movement thereof, a distinctively designed escapement weight adapted to produce `a maximum of effect inthe space allotted, affloating rack to connect the elect of the escapementfmechanism tothe breech bolt in one direction of movement -of the rack but disconnectible -from the escapement mechanism during the return or idling movement ofthe rack, and the pivotal arrangement of the breech bolt engaging pawl provides a pusher type pawl which will insure positive engagement of the breech bolt by the pawl even though a certain amount of wearingof the pawl` takes place.

While the invention has been illustrated and described in its preferred embodiment and has included certain details, it should be understood that the invention is not tobe limited tothe pre` oise details herein illustrated and described since the same may be carried out in other ways, falling n within the scope of the invention'as claimed.

What I claimis: i

1. In combination with an automatic firearm including abreech casing containing a lock frame and a recoil-actuated breech Abolt reciprocable above said lock frame in recoil and counter-recoil directions and 4said firearm also including `means normally urging said breechbolt in counter-recoil direction, mechanism for controlling the rate of firing of said `lirearin and comprising, retarding ases-ieee:

ing mechanism having a relatively wide' rang ofi breech bolt `and said retarding means. toi oppose the force of the means normallyvurging the breech bolt in counter-recoil direction vand thereby `retard the movement of said breech boitin said direction, saidpawl automatically disengag. ing said breech bolt at a Vpredetermined position inthe path of movement of the. breech lbolt 'in counter-recoil direction, a screw adjustably car# ried by said pawl and arranged to 'engage'said member to selectively Vary the amount said porftion 'thereof may pivotally move and project above said lock frame to thereby vary saidv position at l which the pawl automatically disengages said means mounted within said lock.l frame, a member mounted within said lock frame for movement in-opposite directions along`l a xed path extend ing forward and downward, said member being connected to said retarding means, a pawlpivotally' carried by saidmember and having a portion extendingrear'ward of the pivot therefor and normally 'projecting above said lock frame whereby said portion is arranged to engage said breech boltduring the initial partof its `counter-recoil movement to effect connectionbetween the breech bolt and said retarding means to'o'ppose the force of the means normally urgingthe breech bolt in oounter-rec`oil direction'and retard the movement ,c

of said breech bolt in said direction, said pawl automatically disengaging said breech bolt at a predetermined position vin the path of movement of the breech bolt in counter-recoil direction, and a screw adjustably carrie-d by said pawl forward of the pivot therefor and a'rr'angedto engage said member to selectively vary the amount said portion of said pawl may pivotally move and project above said llock frame to thereby vary said posi'- tion at which the pawl automatically disengages said breech bolt.

"2; I'n combination with an automatic firearm includingv a breech casing containing a lock frame and a recoil-actuated breech bolt reciprocable above said lock frame in recoil andV counter-'recoil directions-and said firearm also including means normally urging 'said breech boltin counter-recoil direction, mechanism for controlling the rate of firing of said frearm and comprising, retarding means mounted within said lock frame, a memberfmounted within said lock frame formovementin opposite directions along anx'ed path-extending forward .and downward,v said member being connected to said retarding means, a -pawl pivotally carried by said member and having a portion normally projecting above said lock frame in position to engage said breech bolt during the initial part of its counter-recoil movement to eie'ct connection between the breech bolt, and locking means also carriedl by said pawl and arranged to lock said screw in:` any selected position. e

3..In combination with an automatic firearm including a breech casing-,containinga lockframe and a recoil-actuatedbreechbolt reciprocable above said lock framein recoil and counter-recoil directions and said iirearm also includingy means normally vurgingsaid breech bolt in counter-recoil direction, vmechanism for controlling .the rate of firing of `said rearm and "comprising, retardingV means mounted vwithinV said .lock frame,"a member mounted within ksaid lock frame' `for movement in oppositev directions along a xed path extending forward.. and downward, said member being connectedto said retarding means,l

a pawl pivotally carried by saidmember and having a portion normally .projecting above said lock frame in position to engagesaid breech bolt Jduring the initial part of its counter-recoil move-k ment to effect connection between the breech bolt and said retarding means tooppose the .forceof the means normally urging/the breech boltin counter-recoil direction and thereby retard. vthe movement of said breech bolt in said direction, said-pawl `having a splitthreadedbearing and arranged to automatically. disengage saidhbreech' bolt at a predeterminedlposition'in 'the pathiof movement of the breech bolt in countererecoll direction, a screw adjustably carried; by said split bearing of `saidl pawl andarrang'ed to engage'said member to selectivelyjvary the amount said .portion thereof may .pivotally move and project abovesaid lock lframe to thereby yvary saidzposinonl at ,which the, pawi automaticauy"disengages said breech fbolt,'and a locking screwalso carried by-said pawlrand arranged to tightensald split` bearingaround said'adjustment screw Ato vlock the same in any selectedposition.'

4. In combination with :an .automatic re'arm includingv abreechV casing having.. a .lock :frame therein composedv of a plurality of .members and a breech `boltv mounted for reciprocatingmovementflongitudinally ofsaid breech casing `and also means normally urgingthe ,breechboltfin counter-recoil direction, retarding mechanism mounted inasaid 1ock'.frame andz-includingwa member reciprocably` movable: zinV a` path 'dis-` posed at 4anfangle to the'path' of'movementuof said breechfbolt, means forguidng said Vmovable member with respect to lonetrnember of said lock frame kcomprising; a "pluralityv of slctslam ranged `parallelto eachother and t0 the pathof movement or said movabler Vmember..andI-.clll=z-` posed in one of said members and pinszmounted on the otherof said .members'andslidable in/said slots, for maintaining. :and ir guidingxtlie movable memberin its path, Aandmeans alsofcarried 'by said movable member and; adaptedto engage saioly breech bolt during part. .of the counterrecoil movement .thereof ito cause. the retarding elect `of 'the `retarding mechanism totoppose the force of the means normally urging the breech bolt in counter-recoil direction and subsequently release the breech bolt at a predetermined position in the path of counter-recoil movement to permit the breech bolt to complete its counterrecoil movement independently of said retarding mechanism whereby a retarded rate of re is produced in said rearm,

5. In combination with an automobile rearm including a breech casing having a lock frame therein composed of a plurality o'f members and a breech bolt mounted for reciprocable movement longitudinally of said breech casing and also means normally urging the breech bolt in counter-recoil direction, retarding mechanism mounted in said lock frame and including a member reciprocably movablein a path disposed at an angle to the path of movement of said breech bolt, means for guiding/said movable member with respect to one member of said lock frame comprising a plurality of slots disposed parallel to each other and to the path of movement of said movable member and disposed in one of said members and pins mounted on the other of said members and having heads at one end and removable heads attachable to the other end by snap-acting quick detachable means, said pins being slideably disposed in said slots for maintaining and guiding the movable member in its path and means also carried by said movable member and adapted to engage said breech bolt to move therewith during part of the counter-recoil movement thereof to cause the retarding eect of the retarding mechanism to oppose the force of the means normally urging the breech bolt in counter-recoil direction and subsequently release the breech bolt at a predetermined position in the path of counter-recoil movement to permit the breech bolt to complete its counter-recoil movement independently of said retarding mechanism whereby the retarding mechanism produces a retarded rate of fire in the rearm.

6. In combination with an automatic lirearm including a breech casing and a breech bolt having a plurality of longitudinally spaced pawl engaging vportions thereon and said firearm also having means normally urging the breech bolt in counter-recoil direction, a retarding mechanism including means longitudinally reciprocable in a path extending forward and downward in said breech casing and a member pivotally mounted on said means and normally resiliently urged into position wherein itis adapted to successively engage said pawl engaging portions of said breech bolt to successively connect said movable means to said breech bolt for movement therewith during a part of the counter-recoil movement of said breech bolt to oppose the force of the means normally urging the breech bolt in counter-recoil direction a plurality of times and subsequently release the breech bolt after each of said engagements at predetermined positions in the path of counter-recoil movement of said breech bolt to permit said breech bolt to complete its counter-recoil movement independ- 

